1. Field of the Invention
The present invention relates to a disk drive, and more particularly, to an air bearing slider, which has a read/write head mounted thereon and is lifted from a surface of a disk due to a lifting force generated by the rotation of the disk, and a suspension assembly including the air bearing slider.
2. Description of the Related Art
Hard Disk Drives (HDDs) that can store information in computers read data written on disks or write data on the disks using read/write heads.
FIGS. 1A and 1B are respectively a partial perspective view and a partial side view of a conventional HDD.
Referring to FIGS. 1A and 1B, an HDD includes a disk 10 on which data is written, a spindle motor 15, which rotates the disk 10, and an actuator 20, which moves a read/write head 35 for writing data on the disk 10 or reading data written on the disk 10 to a desired position on the disk 10.
The actuator 20 includes a swing arm 22, which is rotated by a voice coil motor (VCM, not shown), and a suspension assembly 30, which is installed at one end portion of the swing arm 22 and elastically biases an air bearing slider 34, on which the read/write head 35 is mounted, toward a surface of the disk 10.
The suspension assembly 30 includes a load beam 31, which is coupled to the one end portion of the swing arm 22, and a flexure 32, which supports the air bearing slider 34 on which the read/write head 35 is mounted. The air bearing slider 34 with the read/write head 35 thereon is lifted to a predetermined height from the surface of the disk 10 due to a lifting force generated by the rotation of the disk 10, and maintains a predetermined distance between the read/write head 35 and the disk 10. A rear end portion of the flexure 32 is fixed to a surface of the load beam 31, that is, a surface facing the disk 10, by welding or the like, and a front end portion of the flexure 32 moves freely. A dimple 33 is formed on the load beam 31 in such a manner as to protrude toward the flexure 32. A predetermined elastic force is provided to the flexure 32 due to the dimple 33. In the above structure, the flexure 32 can move freely, thereby allowing the air bearing slider 34 attached to the flexure 32 to roll and pitch smoothly.
When the HDD does not operate, that is, when the disk 10 stops rotating, the air bearing slider 34 is parked on a parking zone 11 formed on an inner peripheral side of the disk 10 due to the elastic force of the suspension assembly 30. This head parking method is referred to as a contact start stop (CSS) method.
Further, a ramp loading method may be used instead of the CSS method. In the ramp loading method, a ramp is installed outside the disk and the read/write head is parked on the ramp.
When the HDD is turned on and the disk 10 begins to rotate in a direction D, air starts flowing in a direction A. A lifting force generated due to the air flow is applied to a bottom surface of the air bearing slider 34, that is, an air bearing surface, and thus, the air bearing slider 34 is lifted. At this time, the air bearing slider 34 is lifted up to a height where the lifting force generated by the rotation of the disk 10 becomes equal to the elastic force of the suspension assembly 30. The lifted air bearing slider 34 is moved to a desired position over the disk 10 as the swing arm 22 rotates, and the read/write head 35 mounted on the air bearing slider 34 maintains a predetermined distance from the rotating disk 10 and writes or reads data to or from the disk 10.
The air bearing slider 34 performing the aforesaid function may have various structures. For example, FIG. 2 is a perspective view illustrating a basic structure of a conventional taper flat (TF) air bearing slider.
Referring to FIG. 2, a TF air bearing slider 40 has a thin hexahedral body 42. Two rails 44 extending in a longitudinal direction of the body 42 protrude to a predetermined height from a surface of the body 42, that is, a surface facing the disk 10. Inclined surfaces 46 are formed respectively at front end portions of the two rails 44. In the above structure, if air flows in a direction A due to the rotation of the disk 10, air is compressed at the inclined surfaces 46 such that a positive pressure is applied to surfaces of the two rails 44. A lifting force for lifting the air bearing slider 40 from the surface of the disk 10 is generated due to the positive pressure.
Here, the TF air bearing slider 40 has a problem in that as the number of revolutions per minute (RPM) of the disk 10 increases, the lifting force and the flying height continue to increase. The RPM and the flying height are substantially linearly proportional to each other.
Accordingly, in recent years, a negative pressure (NP) air bearing slider that allows the read/write head to fly at a more consistent flying height over the disk by generating a negative pressure as well as a positive pressure is increasingly popular. FIG. 3 is a perspective view illustrating a basic structure of a conventional NP air bearing slider.
Referring to FIG. 3, an NP air bearing slider 50 includes a body 52, two rails 54, which protrude from a surface of the body 52, that is, a surface facing the disk 10 and extend in a longitudinal direction of the body 52, and a cross rail 58, which is interposed between the two rails 54 and extends widthwise over the body 52. Inclined surfaces 56 are formed at front end portions of the two rails 54, and the cross rail 58 has the same height as the two rails 54. In the above structure, if air flows in a direction A due to the rotation of the disk 10, the two rails 54 generate a positive pressure at both sides of the body 52, and the cross rail 58 forms a negative pressure cavity 59 at a central portion of the body 52. Since the positive pressure is higher than the negative pressure at an earlier stage of the rotation of the disk 10, the air bearing slider 50 is lifted. If the rotational speed of the disk 10 increases, the negative pressure increases. If the rotational speed of the disk 10 reaches a predetermined RPM, the positive pressure and the negative pressure become equal to each other such that the air bearing slider 50 is no longer lifted and is maintained at a constant flying height.
Particles exist in the HDD constructed as described above. The particles attached to the surface of the disk 10 and/or contained in air inside the HDD are conveyed along with the air. When these particles are introduced between the disk 10 and the air bearing slider 34, the particles may cause a scratch or thermal asperity (TA) on the surface of the disk 10, or a damage to the read/write head 35 mounted on the air bearing slider 34, thereby deteriorating the function of the read/write head 35.
To solve the above problem, efforts have been made to improve the cleanliness of the air bearing slider 34, reprocess edges of the air bearing slider 34 to remove chips, maintain a proper flying height of the air bearing slider 34, and/or design the slider 34 so that particles can flow outwardly. Efforts have also been made to improve the cleanliness of a clean room, install a filter for filtering particles inside the HDD, and/or additionally apply a structure for removing particles stuck to the surface of the disk 10 to the HDD.
Nevertheless, the result of those efforts falls short of expectations. Moreover, when the design of the HDD is changed or a new component is added to the HDD, the possibility of problems caused due to the particles is further raised. In particular, the flying height of the air bearing slider 34 is recently decreasing to improve the function of the read/write head 35. Accordingly, the problems due to the particles are becoming more severe.